> I don’t understand why the US voluntarily gave up its significant advantage in manufacturing

We didn't. The US manufactures more than ever. It seems like we gave up the advantage because we let China take over the cheap junk market (before them Japan and Taiwan had that - both have moved up quality though); and we use far less people. A typically factory in 1950 with 2000 workers would now have around 200 to produce the same amount.